Vehicle fuel pump systems commonly employ an electric motor coupled to a mechanical pump for pumping fuel from a fuel reservoir to an engine. Although it is possible to simplify the fuel system controls by operating the electric motor at a sufficiently high speed such that the pump will meet the greatest, fuel demand imposed by the engine, such a simplistic approach may degrade the fuel efficiency of the vehicle (by wasting electrical energy) and adversely effects the life expectancy of the components in the fuel delivery system. In order to operate a fuel delivery system as efficient as possible, it is common for the fuel control system to monitor one or more engine parameters indicative of the real time fuel demand of the engine. Under this controlled, approach, the fuel control system can operate the motor at slower speeds when the fuel demand of the engine is minimal or moderate and the control system can operate the pump motor at higher speeds when the fuel consumption demand of the engine is high. Although such control systems are effective for enhancing the efficiency and life expectancy of the components of the fuel delivery system, they require extra complexity, such as tying the fuel delivery system to the engine or engine control system. This complexity not only increases development costs, but it also increases the cost of implementing the system inasmuch as additional electrical conductors, connectors, and other components must be incorporated into the fuel delivery system.
The present invention provides, among other things, a variable speed motor coupled to a fuel pump, without requiring interconnection of the fuel system to the engine or engine control system for sensing the fuel demands of the engine.